Ms Purdy, who was 39 when she died in 1985, will be remembered with a stone at a churchyard in Grantchester, Cambridgeshire, where she is buried.

The world’s first test-tube baby, Louise Brown, was born in July 1978 after years of research by Cambridge University physiologist Mr Edwards, obstetrician and gynaecologist Mr Steptoe and Ms Purdy, who had trained as a nurse at Addenbrooke’s Hospital in Cambridge.

She had little laboratory experience, but defined the role of the embryologist, developing tasks and processes that are now a standard part of IVF treatments.

Ms Joy remembers her as a “sort-of aunt figure” who spent 10 years working closely with her father.

“She was a key figure in running the labs, and spent time with the patients, reassuring people,” she said. “They weren’t working in easy conditions, her role was hugely important.”

In Mr Edwards’ autobiography, he said they were “a threesome”, describing Ms Purdy as “the patient, indomitable helper without whom none of our work would have been possible”.

He died in 2013 but his family contributed to a crowdfunding site which raised more than £800 for the memorial in Grantchester.